The present invention relates to a diagnosis system for a motor vehicle.
Recently, a motor vehicle has been equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctions of components and sensors occur, the engine does not properly operate.
However, because of the complexity of the electronic control system, it is difficult to immediately find out the trouble. Accordingly, a trouble diagnosis device for easily checking the electronic control system should be equipped in an auto shop.
Japanese Patent Application Laid Open 59-61740 discloses a self-diagnosis system where signaling lamps provided on the vehicle are lit or flashed when abnormalities occur in sensors and actuators such as injectors. However, the actual conditions of the defective sensors and actuators cannot be represented by the lamps.
Japanese Patent Application Laid-Open 58-12848 discloses a diagnosis system in which an exclusive checking, device is provided for measuring the pulse duration of the fuel injection and an engine speed, and for checking whether idling speed is normal. The checking device is provided for diagnosing only designated specific types of motor vehicles.
FIG. 6 shows a recently proposed a diagnosis system which comprises a diagnosis device 102 and a memory cartridge 103 detachably attached to the device 102. The memory cartridge 103 has a memory such as a ROM for storing diagnosis programs and fixed data for the type and the model year of the vehicle 100. Various cartridges 103 for different vehicle types are provided and a cartridge for the presented vehicle is selected and attached to the diagnosis device 102. A two-way communication between the cartridge 103 and an electronic control system 101 on the vehicle 100 is performed for diagnosing the electronic control system. Diagnosis results of sensors are indicated on a display 104 by operating a keyboard 105 on the diagnosis device 102. However, only the numerical value of the result is shown on the display 104 and the name or abbreviation of the component which is being diagnosed is not displayed. Therefore, the diagnostician must keep in mind the selected diagnosis mode or the item of the checking while consulting an operation manual. Thus, the diagnostician cannot concentrate on the diagnosis.